Key-operated fuse-plug



A. c. BECKER. KEY OPERATED FUSE PLUG.

APPLICATION FILED NOV. 10, 199.

UNITED STATES PATENT OFFICE.

ADOL PH RIIFX'JIKER, OF OAKVILLE, CONNECTICUT, ASSIGNOR TO THE CHASE COM- PANIES, INC., 01 WATERBURY, CONNECTICUT, A. CORPORATION.

KEY-OPERATED FUSE-PLUG.

Specification of Letters Patent.

Patented Aug. 16, 1921.

Application filed November 10, 1919. Serial No. 336,924.

To all whom may concern:

Be it known that I, Anonrn G. Rnoxnn, a citizen of the United States, residing at Oakville, in the county of Litchfield and State of Connecticut, have invented a new and useful Improvement in Key-Operated Fuse-Plugs; and I do'hereby declare the following, when taken in connection with the accompanying drawings and the characters of reference marked thereon, to be' a full, clear, and exact description of the same, and which said drawings constitute ing shown as screwed into its protected posi-.

tion in a plug receptacle which is shown partly broken away and in section.

My invention relates to an improved keyoperated self-protecting fuse-plug of the non-removable fuse type, the object being to produce at a low cost for manufacture, a simple and reliable fuse-plug constructed with particular reference to being so embedded in any standard plug-receptacle when in use, that when its key is removed it is protected against being tampered with and also prevented from being removed surre titiously or to meet an emergency.

ith these ends in view, my lnvention consists in a key-operated self-protecting fuse-plug characterized by its adaptation to be screwed by a removable ke into such a position in any standard p ug-receptacle.

that it cannot be removed at will therefrom except by the use of its key or some subst1- tute therefor. sists in akey-operated self-protecting headless fuse-plug characterized by having a relatively short fuse and its mica disk located so close thereto as to render the observation of the fuse easy. My invention further consists in certain details of construction and combinations of parts as will re 1, a plan view of a fuse plug em-' My invention further conbe hereinafter described and pointed out in the claims.

In carrying out my invention as herein shown, I construct what may be aptly termed a half-plug or headless lug inas- 60 much as it 1s made considerab y shorter than the ordinary plu and entirely lacks the finger-grip by whic the ordinary fuseplug is screwed 1nto place in a plug-receptacle and removed therefrom. My improved fuse-plug as compared with fuse-plugs of the prlor art has a relatively short cylindrical body 5 of porcelain or other insulating material its outer end being substantiall fiat and its inner end being slightly conica This body is mounted in a threaded screwshell 6 somewhat shorter than the axial length of the plug-body 5 and having its inner portion threaded. At its inner ed e the said shell is formed with an inward y turned narrow assembly-flange 7, overlapping the edge of the conical inner end of the plug-body which is held against rotation within the shell by its provision with a tangential notch or cut'8 receiving a flatface 9 formed as a art of the assemblyflange 7 as shown in Fig. 2. The outer end of the shell 6 is formed with an'inwardly turned annular retaining-flange 10 which overlaps the edge of a mica window 11 in the shape of a disk which is thus held directly against the flat outer end or .face of the plug-body 5 as shown in Figs. 1 and 4.

The plug-body is traversed by a central fuse-chamber l2 entering its outer end and terminating nearthe apex of its cone in a concentric rivet-hole 13 receiving the prongs 14 of a contact-rivet 15 ofsome other tv such as a standardtubular rivet. e

prongs 14 not only serve to hold the contactrivet 15 in place but also for the attacha ment of the inner end of the fuse 16, the outer end of which lies upon or close to the inner face of the mica window 11 and extends between the same and the flat outer face of the plug-body, its outer extremity being .let into a recess 16 in the edge thereof so as to extend under and make contact with the side wall of the screw-shell 6. The

outer portion of the fuse is thus brought 106 close to the mica-window 11 and therefore so close to the exposed outer end of the plug that when the fuse is blown out it invariably smokes the face of the window and discloses to even casual observation that the 110 plug is dead, whereas in the fuse-plugs of the prior art, the fuse is located so far away from the outer end of the plug and so far away from the mica-window that the fuse does not invariably smoke the window when blown out, leaving the fact to be determined only by a close examination of the plug or even the testing of the same.

I am able to employ a short, headless or half-plug as described, by providing for its insertion and removal by an operating-key made of insulating material and consisting of a hub 17 substantially corresponding in diameter to the diameter of the plug-body 5 and furnished at its outer end with a knurled flange 18. From the inner end of the hub 17 project slotted key-prongs 19 formed by the projecting ends of a wire loop embedded in the hub 17 when the same is molded.

For the reception of the slotted keyprongs 19, the plug-body is formed in its outer face with two key-i101 as 22 located on opposite sides of the fuse-hole 12 and made accessible through corresponding holes 23 in the mica window 11 which is prevented from turning within the flange 10 so as to obstruct the holes 22, by the formation upon the outer face of the plug body 5 of two integral annular bosses concentric with the key-holes 22, the holes 23 in the mica window being large enough to fit over the said bosses 24., whereby the mica window is prevented from turning.

My improved self-protecting headless half-plug is screwed by its removable key into a plug-receptacle screw-shell 25 located within a sleeve 26 projecting from the face of a receptacle-block 2? of any approved construction and design. The receptacle screw-shell 25 has a contact 28 to which the terminal strip 29 leads. My improved halfplug is proportioned in overall length to the length of the screw-shell 25 of a standard fuse-receptacle so that when the plug is screwed into place as described its outer end will be substantially flush with the end of the sleeve 26 thereof as shown in Fig. 6, whereby when its key is withdrawn, the fuseplug is protected against being tampered with and'against removal except with its own key or at some considerable trouble for the improvisation of a key which will answer the purpose. Constructing the plug so that it can only be removed without considerable trouble except by its own key, the plug is protected against removal by an unauthorized person and replacement by a plug of higher capacity is thus guarded against. By preference but not necessarily, the key-prongs 19 are slotted to give the prongs 19 sufficient resiliency for their retention in the key-holes 22 in the plug-body 5 in case it is desired to leave one key in the fuse block. So also, if the fuse-receptacle is in the ceiling, a key having resilient prongs would not'drop out by gravity. Ordinarily the key will be removed and kept in a safe place to prevent tampering with the plugs.

The shortness of my improved headless plug materially cheapens it over the longer plugs of the prior art so that indiscarding the plug when it is dead. there is much less loss, the item of expense chargeable to dead plugs being therefore less with my improved plug than with the non-removable fuse-plugs of the prior art. The key provided with my half-plug may, of course. be used indefinitely. I do not limit myself to the employment of any one key as it is obvious that the form shown may be varied, my invention in this respect being characterized by a headless-plug .adapted to be operated by a removable key of whatever character and design.

I claim:

1. A removable, key-operated, headless, screw fuse-plug comprising a headless plugbody having a fuse-chamber. a screw-shell in which the said body is mounted, a fuse located within the said chamber, and making contact at'its outer end with the said sheil, a contact located at the inner end of the body for the inner end of the fuse, and a mica window closing the outer end of the said fuse-chamber, the said body being adapted in length to substantially fit within the screw-shell of a standard receptacle, and

- being manually removable by means of a removable key.

2. A removable, key-operated, headless, screw fuse-plug comprising a headless plugbody having a fuse-chamber, a screw-shell in which the said body is mounted, a fuse located in the said chamber, and a mica window closing the outer end of the said chamber, the said body being also provided with two parallel key-holes located on opposite sides of the said fuse-chamber for the simultaneous reception of members of a removable key by means of which the plug structure is screwed into and out of the screwshell of a standard screw-shell receptacle within which it fits.

3. A removable, key-operated, headless, screw fuse-plug having a plug-body formed with a fuse-chamber and with two key-holes located on opposite sides thereof and surrounded at their outer ends by concentric bosses, a screw-shell in which the said body is mounted, a fuse located in the said chamber, and a mica window closing the outer end of the said fuse-chamber and formed with holes fitting over the said bosses, whereby the mica window is prevented from rotation and thus obstructing the saidkeyholes, the said body being adapted in length to substantially fit within a standard screwshell receptacle into and out of which it is screwed by means of a removable key.

4. The combination with a removable, key operated, headless, screw fuse plug adapted in length to substantially fit within the screw-shell of a standard. screw-shell receptacle, and having a plug-body formed with a fuse-chamber and with two key-holes located on opposite sides thereof; of a re movable key comprising a flanged-hub of insulating material, corresponding substan tially in diameter to the diameter of the said plug-body, and embedding a'wire loop the ends whereof project from its inner end in which they are separated by the distance separating the key-holes in the headless 15 plug-body.

5. A removable key for a removable, keyoperated, headless, screw fuse-plug, the said key comprising a flanged-hub of insulating material, embedding a loop-shaped wire the ends of which project from the said hub, and are slotted for insertion into key-holes in the body of a removable fuse-plug.

In testimony whereof, I have signed this specification in the presence of two subscribing witnesses.

ADOLPH O. BECKER. 

